Allometric relationships for Quercus gambelii and Robinia neomexicana for biomass estimation following disturbance

In the southwestern USA, increases in size, frequency, and severity of wildfire are driving the conversion of forests to shrub‐dominated ecosystems. Increases in drought extent and severity, coupled with the way that shrub‐dominated systems are perpetuated by high‐severity fire, predisposes these post‐disturbance landscapes to remain in a non‐forest condition. Consequently, understanding the distribution of aboveground biomass in post‐disturbance, shrub‐dominated ecosystems is central to constraining the uncertainty surrounding how these ecosystems interact with light and water to sequester carbon. Here we present allometric regressions for Quercus gambelii (Gambel oak) and Robinia neomexicana (New Mexico locust), two species that dominate post‐fire landscapes in the southwestern USA. Our allometric regressions are designed to be driven by either field plot or high‐resolution remote sensing data, using either shrub area or shrub volume to estimate biomass. Anthropogenic climatic change is increasing the rate and extent of uncharacteristic wildfire across the semi‐arid southwestern USA (Dennison et al. 2014, Singleton et al. 2019). A legacy of fire exclusion has altered the structure of frequent‐fire adapted forests characteristic of the region, increasing the likelihood of high‐severity wildfire (Allen et al. 2002, Singleton et al. 2019). As more of the forested landscape experiences stand‐replacing wildfires, landscape conversion from forest to shrub‐dominated ecosystems is becoming more common (Parks et al. 2014, Coppoletta et al. 2016). Many shrub species re‐sprout following fire, and following high‐severity wildfire, shrubs can become the most abundant, if only woody vegetation, inside the perimeter of high‐severity patches (Savage and Mast 2005, Coop et al. 2016, Guiterman et al. 2018), resulting in large and lasting changes to ecosystem structure and function. The wildfire‐catalyzed reallocation of carbon across the landscape from a vertically stratified coniferous forest canopy to short stature vegetation has significant and lasting implications for how vegetation across the landscape interacts with energy and water to sequester carbon (Amiro et al. 1999, Law et al. 2001, Bowman et al. 2009). Ecosystem light use is substantially reduced following these disturbances due to a combination of the large decrease in leaf area index (LAI) and transition to seasonal oscillation of LAI associated with deciduous plant phenology (Montes‐Helu et al. 2009). Paired with the shorter growing season of deciduous vegetation compared to evergreen canopies, shifts